Unless otherwise indicated herein, the description provided in this section is not itself prior art to the claims and is not admitted to be prior art by inclusion in this section.
In a wireless communication system, a base station may serve user equipment devices (UEs) such as cell phones, wirelessly-equipped computers, tracking devices, embedded wireless modules or the like (whether or not actually “user” operated) over an air interface. In practice, such an air interface may be defined on one or more particular radio frequency channels each spanning a range of frequency spectrum, and the air interface may be divided over time into a continuum of transmission time units, such as frames, subframes, timeslots, symbol durations, and the like, in which communications may pass on a downlink from the base station to the UEs and on an uplink from the UEs to the base station using a designated modulated and encoding scheme. The particular structure of the air interface may be compliant with a wireless wide area network (WWAN) air interface protocol (i.e., radio access technology), such as Orthogonal Frequency Division Multiple Access (OFDMA) (e.g., Long Term Evolution (LTE)), Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), or others now known or later developed.
In such a system, the base station may manage the transmission of data on the downlink and uplink in the defined transmission time units (and in particular resources, such as particular subcarriers, defined in those transmission time units). For instance, as the base station receives data destined to particular UEs, the base station may schedule downlink transmission of that data to occur in particular transmission time units and may transmit the data over the air to the UEs in the scheduled transmission time units. Similarly, as UEs have data to send to the base station, the UEs may send scheduling requests to the base station, the base station may then schedule uplink transmission of that data to occur in particular transmission time units, and the UEs may then transmit the data over the air to the base station in the scheduled transmission time units.
In usual practice, each frequency channel on which a base station serves UEs in such a system would be licensed or otherwise dedicated for use specifically with respect to the air interface protocol on which the base station operates—such as LTE, CDMA, GSM, or the like. Recently, however, there has been a move to allow such base stations to also (or alternatively) make use of unlicensed frequency channels, such as those commonly used for wireless local area network (WLAN) communications like WiFi (e.g., IEEE 802.11 protocols). One example of this, known as LTU-Unlicensed (LTE-U) or LTE Assisted Access (LAA), involves an LTE base station making use of the same frequency channels that are used for WiFi (e.g., 20 MHz wide carriers in the 5 GHz band). With such an arrangement, the base station may thus provide UEs with WWAN service on the same frequency channel that devices in nearby home and business WLANs are using.